Gedcom data structure

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Although this topic appears rather technical, it is very often helpful in working with genealogy to visualize the basic data structure in the Lineage-Linked Gedcom Form, which is the underlying structure in PGV. The data in Gedcom are confined to Records, which can have sub-elements enclosed in them. The top level records live an independent life, and are referenced in other records.

The best example is an Individual (INDI) record, which describes an individual. Each individual has only a single record, all data and references are saved within. The individual can then be shown as a mother in a family, a child in another, an adopted child in a third family, etc., and each time we deal with the same individual (and a single record). Similarly, Family is a top level record.

Top level records in Gedcom

Individual (INDI)
Each person has its own unique record
Family (FAM)
Family record: family consists of at least one parent, typically two, and can have children in different roles.
Multimedia (OBJE)
Each time you add a photograph, document, voice recording or other multimedia file, you are creating a Multimedia Object. The object has a file reference, as well as other attributes like Title, Description, Source etc. The Media visible at different locations (by the person, family, source etc) are in fact references to this single object. You can add more references by editing the Media Object.
Source (SOUR)
Source object contains a description of the source of genealogical data in Gedcom. A book, article, document, email etc. can be a source. While editing individual, family and other records, you always add Source Citation, quoting the Source record and possibly adding the details. Many citations can point to the same source.
Repository (REPO)
Repository is a location where one or many sources are located. It can be an archive, library or your home. The repository record describes how to locate the source, would anybody need to reach it. Multiple sources can point to the same repository.

There are four other top level records: Note (NOTE), Submission (SUBN), Submitter(SUBM) and Header (HEAD), but they do not perform such universal role as those listed above. The Note can be cross-referenced, but in PGV an alternative form is used, embedded in lower level entity. The Submission and Sumbitter play a role only in the file Header to indicate the details in submitting the file to LDS, and are not used in PGV.

While adding the top level records one should always consider, whether the record already exists, and only a reference is needed. In many places an option is presented to either create a new top level record (Multimedia, Source, Repository etc.) or to provide a link to an existing one (with a search function to help). Similarly, an existing person can be linked to a new family (as parent or child) or to an event (as associate) with different roles.

Lower level elements and structures

All other information, dates, facts, addresses, events etc. are entered each time they are needed to describe or complement any of the top level records. In other words, while a Person or Source is unique and described only once in a Gedcom file, the same Location, Residence, School, Fact etc. will be repeated as many times as needed. This suggess some tediousness in entering the same data many times, but PGV has tools to let you search and select some of them (e.g. places) and to copy and paste others (e.g. events and facts).

See also